Susnos on "[Theme: Thematic] responsive theme?"

Hello, there is a beta (Thematic 2.0) available on Github, so it is just around the corner!
If you can't wait there is a very nice starter them (child theme) from Scott Nix that is responsive that you can tweek for yor needs. He has also made another nice childtheme that is more styled and sort of good-to-go. It is called Child´s play.
Best of luck!